Due to the fundamental principle that waves carry energy and momentum with no net mass transport, a particle with different impedance than its host medium will, in general, scatter a portion of an incident wave. The resulting rate of change of both linear momentum and energy density of the wave induces forces on that particle. Previous research has shown that optical or acoustic waves (or beams) can be used to trap single particles within a well or align particles within a flow. For example, “acoustical tweezers” operate by generating a stable potential well with two focused ultrasonic beams propagating along opposite directions. Latex particles were trapped in the potential well and could then be moved axially or laterally by moving one of the focusing transducers that generate the ultrasonic beam. Additional studies show levitation, positioning, and rotation of objects using acoustic waves.